This book focuses on the problematic relationship between legality and legitimacy when a nation (or nations) intervene in the work of other nations. Bringing together a wide range of contributors with a broad set of cases that consider when such intervention is legitimate even if it isn't legal--and vice versa--the chapters cover humanitarian intervention, nuclear nonproliferation, military intervention, international criminal tribunals, interventions driven by environmental concerns, and the export of democracy. By focusing on a diverse array of cases, this volume establishes a clear framework for judging the legitimacy of such actions.